[Octane]

<script>
function ymnojaem(x, y){
    return x * y
}
</script>
<textarea id = "x" cols=1 rows=2></textarea>
<textarea id = "y" cols=1 rows=2></textarea>
<textarea id = "otvet" cols=1 rows=5></textarea>
<button onclick="document.getElementById('otvet').value = ymnojaem(document.getElementById('x').value, document.getElementById('y').value)">умножить</button>